Stud feeding system for welding tools



Sept 1, 1970 l D. E. EHRLICH 3,526,744

STUD FEEDING SYSTEM FOR WELDING TOOLS Filed Oct. 2l, 1968 INVENTOR.

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AT TYB United States Patent O STUD FEEDING SYSTEM FOR WELDING TOOLS DonE. Ehrlich, Avon, Ohio, assignor, by mesne assignments, to TRW Inc.,Cleveland, Ohio, a corporation of Ohio Filed Oct. 21, 1968, Ser. No.769,020 Int. Cl. B231: 9/ 00 U.S. Cl. 219-98 2 Claims ABSTRACT F THEDISCLOSURE Studs to be welded are blown into a loading chamber behind achuck of a stud welding tool and then move into the front of the chuckwhere they are backed up by a plunger. An air nozzle communicates withthe chamber and directs air rearwardly toward a stud fed into thechamber to urge the stud away from the chamber inlet in a manner tosubstantially eliminate stud jamming. The air preferably is suppliedfrom an air cylinder which drives the plunger.

This invention relates to stud welding apparatus and particularly to afeeding system for feeding studs to a chuck of a stud welding tool.

Small studs are now used frequently to fasten objects to workpieces. Thestuds are welded to the workpiece at relatively high rates, sometimesexceeding one per second. To achieve such rates, it is essential thatthe studs be fed automatically to the welding tool chuck. Accordingly,feeding systems previously have been developed for accomplishing thispurpose. These systems generally include a source of a large quantity ofthe studs which are oriented and fed to a supply track communicatingwith an escapement. The escapement transfers the studs individually to aflexible feed tube through which the studs are blown to a loadingchamber of the `welding tool located behind the chuck of the tool. Aplunger located rearwardly of the chamber inlet when a stud is receivedtherein then moves forwardly to hold the stud in the end of the chuckwhen being welded to the workpiece.

When the studs are blown directly into the loading chamber behind thechuck, they tend to bounce considerably. Since the studs are often of alength which differs little from their widest diameter, it is relativelyeasy for the studs to become jammed in the chamber. This produces alengthy interruption in the welding i operation while the stud is freed.It has been found that by maintaining the plunger in a forward positionto block the chamber inlet, when the stud is blown toward the chamber,the stud will hit the plunger, bounce a few times, then rest against theplunger as the air continues to be blown. When the plunger is thenretracted, the stud will move into the chamber with a minimum amount ofadditional bouncing, since the stud moves only a distance approximatelyequal to the diameter of the plunger during its nal travel into thechamber. Minimum bouncing and minimum jamming thereby result.

It has also been found that if a small shoulder is formed in the loadingchamber at the rear of the inlet, the stud will apparently tend toassume a square position as it moves into the chamber to minimize beingcocked as it moves forwardly to the chuck, with jamming furtherdecreased.

While stud jamming is held to a minimum with the above expedients, anoccasional jam will still occur. Even though such is rare, any jammingat all will hamper welding production. In accordance with the invention,a

force is applied to the stud when it enters the loading chamber behindthe chuck to urge the stud away from the chamber inlet and prevent itfrom cocking and jamming as it moves through the chamber into the chuck.Specifically, the force is in the form of an air jet which is directedrearwardly in the chamber against a rear portion of the stud to urge theforward end of the stud away from the chamber inlet. This prevents theforward portion of the stud from catching on the edge of the inlet orotherwise cocking and jamming in the chamber. With the use of theinvention, jamming of the studs when fed to the chuck of the studwelding tool is reduced substantially to zero.

It is, therefore, a principal object of the invention to substantiallyeliminate jamming of the studs when automatically fed from a remotesource to the chuck of a stud welding tool.

Another object of the invention is to apply a force to a stud entering aloading chamber behind a chuck of a stud welding tool in a manner tourge a portion of the stud away from the chamber inlet.

Other objects and advantages of the invention will be apparent from thefollowing detailed description of a preferred embodiment thereof,reference being made to the accompanying drawings, in which:

FIG. 1 is a somewhat schematic view in elevation of a stud welding tooland an automatic stud feeding system embodying the invention;

FIG. 2 is an enlarged, fragmentary view in longitudinal, vertical crosssection of a portion of the welding tool of FIG. l; and

FIG. 3 is a further enlarged, fragmentary view 1n longitudinal, verticalcross section of a loading portion of the tool of FIG. 2.

Referring particularly to FIG. l, a stud weldmg tool 10 is used to endweld small studs to a workpiece in a known manner. The studs arepreferably arc welded by the technique disclosed in Nelson Pat. No.2,191,494 or in Glorioso Pat. No. 3,136,880. The studs can also bewelded, however, by the technique disclosed in Graham Pat. No.2,610,278, by way of example, or by resistance welding.

The stud welding tool 10 includes a main housing 12 of dielectricmaterial having an integral hand grip 14. A chuck assembly indicated at16 is located at the front of the tool and receives, positions, andholds a stud 18 during the welding operation. The chuck assembly 16 issurrounded by a suitable spark shield 20v attached to a welding foot 22which is adjustably held by two supporting legs 24.

The chuck assembly 16 is attached to the front of a chuck leg 26 whichlincludes an air cylinder 28 and a solenoid core 30 at the rear thereof.Welding current is supplied to the stud 18 from a main :flexible weldingcable 32 through the chuck leg 26 and the c huck assembly 16.

The solenoid core 30 extends rearwardly into a lifting and holding coil`314 and the core 30 along with the chuck leg 26 and the chuck assembly16 is retracted when current is supplied to the coil' 34 through aflexible control cable 36. The rearward movement of the core 30, whichdetermines the extent of the lift o-f the chuck assembly 16 and the stud18, is limited by an adjustable core piece 38. A return or plungerspring 40 returns the stud to the workpiece when the power to the coil34 is shut olf.

The overall feeding system includes a source 42 of studs shown in theform of a vibratory hopper which carries the studs by a vibratory motionup a spiral track therein, orients them, and feeds them intoan inclinedsupply track 44. The studs are sequently fed to an escape.- ment 46which transfers the studs individually to a flexlble supply tube 48having an internal passage 50 simllar in shape to but slightly larger insize than the transverse sectional shape of the studs 18. The studs 18are then blown sideways through the flexible tube 48 to the welding toolby air supplied through a line 52 and controlled by a valve 53.

The tube 48 connects with a rigid fitting 54 which is releasably heldIby a quick-release mounting indicated at 56 at the forward end of thewelding tool. The exit end of the fitting 54, which also has a passagesimilar to the passage 50, communicates with a T-shaped loadchamberinlet 58 (FIGS. 2 and 3) for a loading chamber 60 formed in a chuckadapter or holder 62 which is connected with the forward end of thechuck leg 26 and forms part of the assembly 16. An annular shoulder 63(FIG. 3) also preferably is located in the chamber 62 to the rear of theinlet 58. A chuck 64 is suitably connected to the adapter 62 as by athreaded connector 66. The chuck 64 has a passage 68 thereincommunicating at the rearward end with the loading chamber 60 and at aforward end with bifurcated chuck jaws 70.

When the stud 18 is received in the loading chamber 60 through the inlet58, it moves forwardly into the jaws 70 and is then backed up with theforward end projecting beyond the jaws by a plunger 72. The plunger 72extends rearwardly through the adapter 62 and through a sealing member74 tothe air cylinder 28 where it is connected with a piston 76. The aircylinder is double-acting with air supplied to the rear or blind end ofthe piston by a line 78 and with air supplied to the forward or rod endof the cylinder through a line 80.

In accordance with the invention, when the stud 18 enters the chamber60, a force is applied to the stud tending to urge the forward end awayfrom the forward edge of the inlet 58. For this purpose, a diagonalpassage or nozzle 82 is formed in the adapter and is positioned so thata jet or stream of air issuing therefrom has a rearward component. Thepassage preferably is located at an angle of -60 to the axis of thepassage 68 and the chamber 60 and is positioned diametrically oppositethe inlet 58. Any angle is satisfactory if the rearward component of thejet is sufficient to control the position of the stud and the downwardforce of the jet is not strong enough to blow the stud back through theinlet. The air issuing from the nozzle contacts the underside of a rearportion or head 84 of the stud 18, tending to rotate it in a clockwisedirection, as shown, to urge a forward portion or stem 86 of the studupwardly and away from the forward edge of the inlet 58. The air isapplied through the nozzle for a period of a fraction of a second whichis the period of time the air is applied to the forward end of thecylinder 28 to move the piston and plunger rearwardly and hold theplunger rearwardly while the stud enters the chamber.

While the air can be supplied from various sources for the nozzle orpassage 82, it is most expeditious to supply the air from the rod end ofthe cylinder 28 since this requires a minimum of additional productionsteps and utilizes air that is already required for the operation of thetool. Accordingly, a rearwardly-extending passage 88 is formed in theadapter 62 with the forward end communicating with the passage 82 andthe rearward end terminating in a recess 90 of the adapter into whichthe sealing member 74 is threaded. The sealing member 74 has atransverse passage 92 through which air can pass from the forward end ofthe cylinder 28 and an annular passage 94 in the sealing member 74 tothe passages 88 and 82.

With this source of air, the diameter of the passage 82 has been foundto be satisfactory when in a range of 0.016 to 0.028 inch or larger withthe diameter of the passage 88 being from fgg inch to 1/15 inch and withthe air supplied to the cylinder 28 being 80 p.s.i.g. The

passages can be larger but no improvement in operation results and moreair is consumed.

With this application of force to the stud, a substantial reduction injamming has been found to result. For example, in one series of tests,100,000 of the studs 18 were fed to the loading chamber and chuck of awelding tool with air applied against the stud as it enters the chamber,as shown, without any jamming whatsoever occurring. The air passage 82was then blocked and 2000 additional studs were fed to the tool withjamming occurring on the average of once every studs. The passage wasthen opened again, and another 100,000 studs fed to the tool without anyjamming at all.

While the operation of the system embodying the invention will beapparent from the above description, it will be reviewed briefly. Whenthe plunger 72 is in the forward position near the jaws 70 of the chuck64, a four-way valve 96 supplies air to the rear of the cylinder 28. Theescapement 46 is then operated to transfer a stud to the mouth of theflexible tube 48, at which time the valve 53 is opened to blow the studthrough the tube 48, through the fitting 54, and into the inlet 58against the side of the plunger 72. The stud hits the side of theplunger and bounces a few times, coming to rest against the plunger withair continuing to be blown through the tube 48 from the line 52. Thevalve 96 is operated to supply air to the forward end of the cylinder 28to retract the plunger 72 to the position shown in FIG. 2 with the endof the plunger 72 behind the inlet 58. At this time, the stud will moveinto the loading chamber 60, the final distance which is equalapproximately to the diameter of the plunger 72. Since this travel issmall, little if any bouncing of the stud 18 will result.

When the air is supplied to the forward end of the cylinder, it also issupplied through the passage 88 and the passage 82 into the loadingchamber 60 so that it strikes the rear portion or head 84 of the stud 18when in the chamber. This tends to move the stem 86 upwardly away fromthe forward edge of the inlet 58 and prevents the stem 86 fromcontacting the forward edge of the inlet 58 and cocking or jamming.After the stud has entered the chamber 60, the valve 96 is operated tosupply air again to the rear end of the cylinder 28 to move the piston78 forwardly and cause the plunger 72 to move forwardly and back-up thestud 18 in the position in which the stem 86 projects from the chuck 64,at which time the stud is ready to be welded to the workpiece.

Various modifications of the above described embodiment of the inventionwill be apparent to those skilled in the art and it is to be understoodthat such modifications can be made without departing from the scope ofthe invention since the embodiment described and shown is primarily forpurposes of illustration rather than limitation.

I claim:

1. Apparatus for welding a stud having a head and a stern, saidapparatus comprising a chuck having a substantially cylindrical passagetherein, loading means behind said chuck for loading said chuck, saidloading means having a chamber communicating with said passage, saidloading means having a stud inlet communicating with said chamber, meansforming a feed passage aligned with said stud inlet in one position ofsaid loading means, said feed passage having a contour similar in shapeto the longitudinal cross-sectional shape of the stud for directing thestud sideways into said stud inlet with the stem of the stud facingforwardly toward said chuck, means for connecting the chuck to a powersource for effecting a weld between the stud and a workpiece, a plungerassociated with said loading means for holding a stud in the chuck whena weld occurs, said plunger also having a rearward position behind thestud inlet, a piston connected to said plunger, an air cylinder in whichsaid piston moves, means for supplying air to the forward end of saidcylinder for moving said piston in a direction References Cited awayfrom said chuck, fluid passage means connecting the forward end of saidcylinder with said loading cham- UNITED STATES PATENTS ber, said fluidpassage means being positioned relative gl'ieslt a1- to said chamber todirect air with a rearward component against the stud in a manner tourge the stern of the o 3,309,495 3/1967 ShOuP et 3L 219"98 tliadmgayfrom the stud inlet when received 1n sald JOSEPH VTRUHEPmary Examiner 2.Apparatus according to claim 1 characterized by ROBERT ONEILL, AssistantExaminer the air passage being positioned to direct the air at an 10angle of not more than 60 to the axis of said chuck US Cl- X-R passage.219-99

